Customer networks are networks established by individuals or companies for internal communication. Customer networks may include local area networks (LANs) or wide area networks (WANs) that comprise a plurality of subscriber devices, such as personal computers, laptops, workstations, personal digital assistants (PDAs), wireless devices, network-ready appliances, file servers, print servers or other devices. The customer networks may meet customer-specific needs using one or more Layer 2 communication protocols, such as an Asynchronous Transfer Mode (ATM) protocol, an Ethernet protocol, a Bridged Ethernet protocol, a Frame Relay protocol.
These layer 2 protocols may transfer information in fixed-length data units, such as frames or cells. To transfer the data units, switches within a customer network often create a fixed network path, referred to as a virtual circuit. The frames transmitted by a source device within the customer network travel along the virtual circuit created by the switches. A destination device receives the data units from the virtual circuit, and reassembles the information from the data units.
Another popular network technology is the Internet Protocol (IP) networking protocol in which information is divided into variable-length blocks called packets. In contrast to fixed data unit protocols, such as the ATM protocol, IP-based networks individually route these packets, also referred to as “datagrams,” across the network from a source device to a destination device. In other words, unlike the virtual circuits within a customer network, each packet can take a different route from the source to the destination device within the IP network. The destination device reorders the packets upon receipt, extracts the information from the packets, and assembles the information into its original form.
In order to allow remote customer networks to communicate, IP-based communication techniques are being developed that relay frames through one or more intermediate IP network, such as the Internet. According to these communication techniques, routing devices near an edge of the IP network, often referred to as edge routers, can receive frames from one of the customer networks via an L2 protocol, encapsulate the frames within packets, and route the packets through the IP network to the other customer network. Routing devices within the IP network maintain tables of routing information that describe available routes through the network.
Upon receiving an incoming packet, the routing device examines information within the packet and forwards the packet in accordance with the routing information. Some conventional systems use Multi-protocol Label Switching (MPLS) protocols to transport the L2 traffic through the intermediate networks. MPLS is a mechanism used to engineer traffic patterns within Internet Protocol (IP) networks. By utilizing MPLS, a source network device can request a static path through a network, i.e., a Label Switched Path (LSP), to carry MPLS packets from the source network device to a destination network device.
In some cases, a router within an IP network may receive a join request for a multicast group from a subscriber device within a customer network. When the router receives the L2 multicast traffic associated with the multicast group from a source network, the router forwards the multicast traffic to the requesting subscriber device. When two or more subscriber devices connected to the same router request to join the same multicast group, the source device sends an identical copy of the associated multicast traffic to the router for each of the requesting subscriber devices over the same connection. This is not bandwidth efficient as multicast traffic typically comprises high bandwidth data, audio, or video streams.